Current work focuses on the following three topics. (1) Common structural models for protein-nucleic acid interactions in ribosomal, repressor, histone, and plant viral proteins are being investigated through amino acid sequence comparisons, helical wheels, and secondary structure prediction. (2) The amino acid distribution in particular sequence positions within the surrounding protein secondary structures is under examination in an attempt to improve secondary structure prediction methodologies and to identify side group physico-chemical characteristics essential in the formation of secondary structural types. (3) Amino acid exchanges between halophilic and non-halophilic ferredoxins and their relationship with the known tertiary structure of S. platensis ferredoxin are being studied to elucidate further the physical principles of structural stability in high-salt environments. The amino acid composition of other halophilic proteins is also under scrutiny.